Relevance of increased lung thallium uptake on stress imaging in patients with unstable angina and non-Q wave myocardial infarction: results of the Thrombolysis in Myocardial Infarction (TIMI)-IIIB Study.

OBJECTIVES

This study sought to determine the significance of abnormal thallium-201 (Tl-201) lung uptake on stress imaging in the absence of perfusion abnormalities.

BACKGROUND

Abnormal Tl-201 lung uptake, represented by an increased lung/heart ratio (LHR), on stress imaging is a marker of stress-induced left ventricular dysfunction and poor prognosis in patients with coronary artery disease.

METHODS

We evaluate 1,271 patients from the Thrombolysis in Myocardial Infarction (TIMI)-IIIB trial (86% of TIMI-IIIB cohort) with unstable angina or non-Q wave myocardial infarction, who underwent predischarge exercise (92%) or dipyridamole stress (8%) Tl-201 imaging. An increased LHR (> or = 0.50) was related to perfusion abnormalities and adverse cardiac events at 1 year.

RESULTS

Of 1,271 patients, there were 762 (60%) with and 509 (40%) without perfusion abnormalities. An increased LHR was seen in 227 patients (18%) (173 [23%] with, 54 [11%] without perfusion abnormalities). Patients with an increased LHR had a lower left ventricular ejection fraction, higher body weight, lower exercise capacity and a higher prevalence of angina on exercise than patients with a normal LHR. In the two groups with increased LHR, there was no difference in age, hypertension, previous myocardial infarction, total exercise time, frequency of angina and ST segment depression on exercise. However, the group with an increased LHR and normal myocardial perfusion had a preponderance of women (65% vs. 30%, p < 0.001). At 1-year follow-up, patients with an increased LHR had a higher cardiac event rate than those with a normal LHR (18% vs. 10%, respectively, p = 0.001) despite a higher revascularization rate (28% vs. 15%, p < 0.001). An increased LHR was associated with increased adverse cardiac events, irrespective of the presence or absence of perfusion abnormalities.

CONCLUSIONS

An increased LHR continues to be associated with higher adverse cardiac events in the current era of aggressive interventional management of coronary artery disease. An increased LHR in the absence of myocardial perfusion abnormality is seen mostly in women and overweight patients. However, despite the apparent absence of perfusion abnormalities, an increased LHR in this group is also associated with a higher rate of adverse cardiac events.